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Notes: We present recent experimental results of difference-frequency generation (DFG) and sum-frequency generation (SFG) from zincblende materials. We measure the radiation field of difference-frequency generation and the radiation intensity of sum-frequency generation versus crystallographic orientation and fundamental photon energy. The simultaneous measurement of the angular dependence of polarized DFG and SFG is well characterized by the bulk second-order nonlinearity calculation. Pronounced resonant behaviors near the GaAs band gap for both radiations (DFG and SFG) are compared.

Notes: We report the study of optically induced terahertz (THz) electromagnetic radiation from 〈110〉 oriented zinc-blende crystals. This work extends our previous studies of 〈100〉 and 〈111〉 GaAs. Excellent agreement between calculated results and experimental data indicates that, under conditions of moderate optical fluence and normal incidence on the unbiased sample, second-order optical rectification is the major nonlinear process that generates THz radiation.

Notes: We report optical rectification and subsequent generation of subpicosecond submillimeter-wave radiation from a nonlinear organic crystalline salt. With optical excitation at a wavelength of 820 nm and a 150 fs pulse duration, the magnitude of the rectified field from the organic salt dimethyl amino 4-N-methylstilbazolium tosylate is one and two orders of magnitude larger than that from GaAs and LiTaO3 crystals, respectively. This organic crystal presently provides the most intense terahertz radiated field among all of the natural nonexternally biased materials we know.

Notes: We report the measurement of optically generated THz radiation from over ten different metal/GaAs interfaces. We observe an anomalous behavior in the THz beams emitted from these interfaces. In contrast to THz radiation generated at normal incidence where the amplitude of the THz signal decreases with increasing metal film thickness, at oblique incidence we observe increased THz emission with increasing metal thickness until reaching a maximum near 80 A(ring).

Notes: We report the results of coherent measurement (phase and amplitude) of optical rectification from a variety of electro-optic crystals. We also present a comparison of the experimental data with a theoretical calculation.

Notes: The bonding structure of an amorphous fluoropolymer, AF 1600, with Al, Ag, Au, and Cu were examined using x-ray photoelectron spectroscopy. 100 A(ring) thick films of AF 1600 were deposited on various metal films. AlF3 was found at the AF 1600/Al interface. F detached from the −CF3 functional group of the AF 1600, diffused into the Al/Al2O3 matrix and formed AlF3. The diffusion depth of F is estimated to be (approximately-greater-than)150 A(ring). An Al film was evaporated onto an AF 1600 film. The Al film was then mechanically peeled off and the remaining polymer surface examined. AlF3 was again found. For the spin-on AF 1600 film on Ag, Au, and Cu, no chemical reaction between the metal and the polymer were found.

Notes: Novel nonlinear composite thin films containing 4-dialkylamino-4'-nitro-stilbene (DANS) and Teflon AF 1600 have been deposited by vacuum evaporation techniques. Pure DANS thin film, due to its centrosymmetric crystal structure, does not exhibit any electro-optic effect. However, composite thin films of DANS and Teflon AF 1600 with a DANS concentration of 5%–25% (by volume) do exhibit an electro-optic effect after poling. Their electro-optical coefficients are measured to be as large as 2.4 pm/V. X-ray diffraction shows that these composite thin films are in an amorphous state as-deposited as well as after poling. It is argued that the DANS molecules are in their molecular form embedded in the Teflon AF amorphous matrix, thereby allowing the effect of their large molecular hyperpolarizability to be detected. The characterization of the thin films using scanning electron microscopy is also presented.

Notes: Elastic dislocation theory has been modified to determine 3-D subsurface displacements for faults in a three-layer elastic-gravitational medium. A new set of kernel functions for Fourier-Bessel integrals describing subsurface displacements have been derived, using the Thomson-Haskell propagator matrix technique, and has been used to investigate the effect of layering and gravity on subsurface displacement fields. Within our three-layer model, layer 1 may be used to represent the seismogenic upper crust, layer 2 the ductile lower crust and layer 3 the ductile mantle.For a point source within the upper layer, lower layer rigidity moduli control the amplitude and wavelength of displacements within the upper layer and the relative distribution of uplift and subsidence within foot and hanging wall. Displacement variations, due to lower layer rigidity moduli changes, increase with depth and are profound at the base of the upper layer and within the lower layers. High-rigidity-moduli lower layers attenuate the upper layer displacement field, while a decrease gives amplification. The effect of gravity on the subsurface displacement field is more pronounced when the rigidity of the lower layers is small.The elastic-gravitational dislocation model has been used to examine co-seismic and post-seismic components of surface and subsurface displacement during extension of continental lithosphere. The model predicts surface co-seismic footwall uplift and hanging-wall subsidence; the co-seismic subsidence being greater than the uplift. Post-seismic relaxation of stress within the lower crust and mantle by post-seismic ductile deformation, gives an increase in footwall uplift and a decrease in maximum hanging-wall subsidence within the upper layer. A decrease in upper layer rigidity due to post-seismic brittle or plastic deformation within the upper crust leads to a decrease in the wavelength of surface footwall uplift and hanging-wall subsidence. The elastic-gravitational dislocation model has also been used to investigate the development of Moho topography during continental extension. Co-seismically Moho under footwall is predicted to uplift, while that under hanging wall subsides but by a smaller magnitude. During post-seismic relaxation Moho topography is predicted at first to increase in magnitude and then to decay. The existence of preserved Moho topography uplift associated with old continental rifts implies a finite long-term ductile strength within the lower crust and mantle.

Notes: A quantitative model using elastic dislocation theory has been developed to model the near-field subsurface displacement field associated with faults and fault arrays within an elastic layer above an elastic half-space. A fault is modelled as a surface across which there is a discontinuity in prescribed displacements. Fault displacements may be oblique as well as dip-slip. The mathematical expressions for the surface and subsurface displacements are formed using the Thomson-Haskell matrix technique. Faults may intersect the free surface or may be blind. The model has been used to determine the 3-D surface and subsurface displacement fields for a rectangular fault with constant slip and for an elliptical fault on which the slip varies from a point of maximum displacement at the centre to zero displacement at an elliptical tip-line. The 3-D displacement field and associated strain tensor may be determined for individual slip events on a fault or for cumulative fault displacements. Displacement contour maps may be constructed for either originally horizontal, vertical or inclined horizons. The model has also been applied to multiple fault arrays.